Light emitting element

ABSTRACT

A light emitting element includes a semiconductor structure, and first and second electrodes. In a plan view, the first electrode has a first connecting portion, and a first extending portion and exactly two second extending portions. The second electrode has a second connecting portion, and exactly two third extending portions. The first extending portion extends linearly from the first electrode connecting portion toward the second electrode connecting portion. Each of the two third extending portions includes a bent portion, and a linear portion located between the first extending portion and a respective one of linear portions of the two second extending portions, and along an imaginary line that extends through the two second extending portions and the two third extending portions in a direction perpendicular to the direction in which the first extending portion extends, an entirety of the second electrode is located inward of the two second extending portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.16/785,143, filed on Feb. 7, 2020, which is a continuation applicationof U.S. patent application Ser. No. 16/351,206, filed on Mar. 12, 2019,now U.S. Pat. No. 10,593,840, which is a continuation application ofU.S. patent application Ser. No. 15/835,175, filed on Dec. 7, 2017, nowU.S. Pat. No. 10,276,751, which is a continuation application of U.S.patent application Ser. No. 15/399,196, filed on Jan. 5, 2017, now U.S.Pat. No. 9,882,093, which is a continuation application of U.S. patentapplication Ser. No. 14/560,224, filed on Dec. 4, 2014, now U.S. Pat.No. 9,577,152. This application claims priority to Japanese PatentApplication No. 2013-254243 filed on Dec. 9, 2013 and Japanese PatentApplication No. 2014-236462 filed on Nov. 21, 2014. The entiredisclosures of U.S. patent application Ser. Nos. 16/785,143, 16/351,206,15/835,175, 15/399,196 and 14/560,224, and Japanese Patent ApplicationNos. 2013-254243 and 2014-236462 are hereby incorporated herein byreference.

BACKGROUND Technical Field

The present disclosure relates to a light emitting element, andparticularly to an electrode structure of the light emitting element.

Related Art

There have been made various developments to obtain a uniform emissionfrom a light emitting element. For example, for a light emitting elementhaving a quadrilateral outer shape, electrode structures in which eithera second electrode or a first electrode is disposed at a center portionof an upper surface of a light emitting element, and the other electrodeis disposed embracing it (for example, JP 2011-61077 A, JP 2012-89695 Aand JP 2011-139037 A).

Each of those various electrode structures is proposed aiming to obtaina uniform distribution of current density to obtain a uniform emissionover the entire surface of the light emitting element. However, evenwith those structures, a deviation in the distribution of currentdensity within a region disposing between the second electrode and thefirst electrode occurs, which may cause concern of insufficient forobtaining a uniform emission.

SUMMARY

Accordingly, the present disclosure is devised to solve the problems asdescribed above, and is aimed to provide a light emitting elementreducing uneven distribution of the current density between theelectrodes.

The present disclosure relates to a light emitting element. The lightemitting element according to one aspect includes a semiconductorstructure, and first and second electrodes formed above thesemiconductor structure. In a plan view, the first electrode has a firstconnecting portion configured to be bonded with a first conductive wire,and exactly three extending portions extending from the first electrodeconnecting portion, the three extending portions being a first extendingportion, and exactly two second extending portions. The second electrodehas a second connecting portion configured to be bonded with a secondconductive wire, and exactly two third extending portions extending fromthe second connecting portion. The first extending portion extendslinearly in a direction from the first electrode connecting portiontoward the second electrode connecting portion. Each of the two secondextending portions includes a bent portion, and a linear portion thatextends in a direction substantially parallel to the direction in whichthe first extending portion extends. Each of the two third extendingportions includes a bent portion, and a linear portion that extends in adirection substantially parallel to the direction in which the firstextending portion extends and that is located between the firstextending portion and a respective one of the linear portions of the twosecond extending portions, and along an imaginary line that extendsthrough the two second extending portions and the two third extendingportions in a direction perpendicular to the direction in which thefirst extending portion extends, an entirety of the second electrode islocated inward of the two second extending portions.

A light emitting element according to another aspect includes asemiconductor structure, and first and second electrodes formed abovethe semiconductor structure. In a plan view, the first electrode has afirst connecting portion configured to be bonded with a first conductivewire, and exactly three extending portions extending from the firstelectrode connecting portion, the three extending portions being a firstextending portion, and exactly two second extending portions. The secondelectrode has a second connecting portion configured to be bonded with asecond conductive wire, and exactly four extending portions extendingfrom the second connecting portion, the four extending portions beingexactly two third extending portions, and exactly two fourth extendingportions. The first extending portion extends linearly in a directionfrom the first electrode connecting portion toward the second electrodeconnecting portion. Each of the two second extending portions includes abent portion, and a linear portion that extends in a directionsubstantially parallel to the direction in which the first extendingportion extends. Each of the two third extending portions includes abent portion, and a linear portion that extends in a directionsubstantially parallel to the direction in which the first extendingportion extends and that is located between the first extending portionand a respective one of the linear portions of the two second extendingportions. Each of the two fourth extending portions includes a bentportion, and a linear portion that extends in a direction substantiallyparallel to the direction in which the first extending portion extends.Each of the two second extending portions is located between arespective one of the linear portions of the two third extendingportions and a respective one of the linear portions of the two fourthextending portions.

With the light emitting element according to the present disclosure,uneven distribution of the current density between the electrodes can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view showing a light emitting element according toEmbodiment 1 of the present disclosure;

FIG. 1B is a plan view showing a Modification Example 1 of the lightemitting element according to Example 1 of the present disclosure;

FIG. 1C is a schematic cross-sectional view showing the light emittingelement according to Example 1 of the present disclosure;

FIG. 1D is a plan view showing another Modification Example of the lightemitting element according to Example 1 of the present disclosure;

FIG. 2A is a plan view showing a light emitting element according toExample 2 of the present disclosure;

FIG. 2B is a plan view showing a Modification Example of the lightemitting element according to Example 2 of the present disclosure;

FIG. 3 is a plan view showing a light emitting element according toExample 3 of the present disclosure;

FIG. 4 is a plan view showing a light emitting element according toExample 4 of the present disclosure;

FIG. 5 is a plan view showing a light emitting element according toExample 5 of the present disclosure;

FIG. 6 is a plan view showing a light emitting element according toExample 6 of the present disclosure;

FIG. 7 is a plan view showing a light emitting element according toExample 7 of the present disclosure;

FIG. 8 is a plan view showing a light emitting element according toExample 8 of the present disclosure;

FIG. 9 is a plan view showing a light emitting element according toExample 9 of the present disclosure;

FIG. 10 is a plan view showing a light emitting element according toreference; and

FIG. 11 is schematic plan views showing distribution of current densityof light emitting elements according to Example 1, 5 and 8 andreference.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments for implementing the light emitting element of the presentdisclosure will be described below with reference to the accompanyingdrawings. The sizes and the arrangement relationships of the members ineach of drawings are occasionally shown exaggerated for ease ofexplanation. Further, in the description below, the same designations orthe same reference numerals may, in principle, denote the same or likemembers and duplicative descriptions will be appropriately omitted. Inaddition, a plurality of structural elements of the present disclosuremay be configured as a single part which serves the purpose of aplurality of elements, on the other hand, a single structural elementmay be configured as a plurality of parts which serve the purpose of asingle element. Further, constitutions described in some of examples andembodiments can be employed in other examples and embodiments.

The light emitting element of the present disclosure has a firstconductivity type semiconductor layer, a second conductivity typesemiconductor layer, a first electrode formed on the first conductivitytype semiconductor layer, and a second electrode formed on the secondconductivity type semiconductor layer. The first electrode and thesecond electrode are disposed on the same face side of the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer.

Here, the first conductivity type semiconductor layer and the secondconductivity type semiconductor layer have different types ofconductivity. The first conductivity type semiconductor layer may beeither n type or p type. The second conductivity type semiconductorlayer is p type if the first conductivity type semiconductor layer is ntype, and vice versa.

(First Conductivity Type Semiconductor Layer and Second ConductivityType Semiconductor Layer)

The first conductivity type semiconductor layer and the secondconductivity type semiconductor layer are members that serve as lightemitting components in a light emitting element, and are usually stackedto constitute a semiconductor stack. The first conductivity typesemiconductor layer and the second conductivity type semiconductor layermay each have a single-layer structure, or may have a laminatedstructure. In the case of a laminated structure, not all of the layersthat make up the first conductivity type semiconductor layer and thesecond conductivity type semiconductor layer need to exhibit the firstor second conductivity type. Usually, an active layer (light emittinglayer) is disposed between these semiconductor layers. The active layermay have either a multiple quantum well structure or a single quantumwell structure formed in a thin-film that produces a quantum effect. Ofthose structures, a structure having the first conductivity typesemiconductor layer, the active layer, and the second conductivity typelayer stacked in that order is preferably employed. In other words, itis preferable to stack the n-type semiconductor layer, the active layer,and the p-type semiconductor layer, in that order. The p-typesemiconductor layer side here is the side where the first electrode andsecond electrode are disposed.

There are no particular restrictions on the type or material ofsemiconductor layer, but a nitride semiconductor material such asIn_(X)AlGa_(1-X-Y)N (0≤X, 0≤Y, X+Y≤1) can be used to advantage, forexample.

The first conductivity type semiconductor layer and the secondconductivity type semiconductor layer are formed on a substrate.Examples of the material for the substrate include an insulatingsubstrate such as sapphire (Al₂O₃) and spinel (MgAl₂O₄), siliconecarbide (SiC), ZnS, ZnO, Si, GaAs, diamond, and an oxide substrate suchas lithium niobate and neodymium gallate which are capable of forming alattice matching with the nitride semiconductor. The substrate used forgrowing the semiconductor layers may be removed from the semiconductorstack,

The first conductivity type semiconductor layer and the secondconductivity type semiconductor layer are such that the first electrodeand second electrode (discussed below) are disposed on the same faceside of the first conductivity type semiconductor layer and the secondconductivity type semiconductor layer, so either the second conductivitytype semiconductor layer is laminated on the first conductivity typesemiconductor layer so as to expose part of the first conductivity typesemiconductor layer, or the first conductivity type semiconductor layeris laminated on the second conductivity type semiconductor layer so asto expose part of the second conductivity type semiconductor layer.

In an embodiment, a semiconductor stack is constituted by laminating ap-type semiconductor layer via the active layer over an n-typesemiconductor layer, and the p-type semiconductor layer and the activelayer are partially removed so as to expose part of the n-typesemiconductor layer beneath them.

There are no particular restrictions on the semiconductor stack thatserves as the light emitting component of the light emitting element,but the plan view shape is preferably one having a pair of opposingsides, and a rectangular shape is more preferable. The corners, however,may be rounded off. With a rectangle, variation in the angle of the fourcorners of about 90±10 degrees is permissible. With a square, variationin the length of one side of about ±5% of the length of the other sidesis permissible.

(First Electrode and Second Electrode)

The first electrode and the second electrode supply current to the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer, respectively, and are therefore directly orindirectly electrically connected to the first conductivity typesemiconductor layer and the second conductivity type semiconductorlayer.

The first electrode is an n side electrode if the first conductivitytype semiconductor layer is n type, and the first electrode is a p sideelectrode if the first conductivity type semiconductor layer is p type.This is similar as to the second electrode.

In a plan view, the first electrode and the second electrode arearranged at the inner side of the light emitting element. In otherwords, it is preferred that the first electrode is surrounded by thesecond conductivity type semiconductor layer, or the second electrode issurrounded by the first conductivity type semiconductor layer. With thisarrangement, electric current can be diffused all around the firstelectrode or the second electrode. Part of the first electrode or thesecond electrode may not be surrounded by the first conductivity typesemiconductor layer or the second conductivity type semiconductor layer.

All or part of the first electrode may be surrounded by the secondelectrode, or vice versa. In other words, all or part of the n-sideelectrode may be surrounded by the p-side electrode, and all or part ofthe p-side electrode may be surrounded by the n-side electrode. Theformer is especially preferable when ensuring the proper surface area ofthe active layer is taken into account.

The first electrode and second electrode respectively have the firstconnecting portion and second connecting portion.

The first connecting portion and second connecting portion are so-calledpad electrodes that are connected to external electrodes, externalterminals, or the like to supply current to the light emitting element,and are portions where a conductive wire or the like is bonded, forexample.

The first connecting portion and second connecting portion areeccentrically located on a pair of opposing sides of the semiconductorstack. In particular, when the plan view shape of the semiconductorstack is rectangular, the first connecting portion and second connectingportion are preferably disposed near the respective ends of a centerline. This center line is a line parallel to one side of the plan viewshape of the semiconductor stack, and is preferably a line passingthrough the center point of another side perpendicular to this one side.This center line will sometimes be referred to as the first center line.In this Specification, however, it is permissible for the center line,center point, and so forth to vary from about a few microns to a fewdozen microns due to machining precision of the light emitting elementand so forth.

The plan view shapes of the first connecting portion and the secondconnecting portion can be adjusted appropriately according to the sizeof the light emitting element and the arrangement of the electrodesetc., and for example, a circular shape, a polygonal shape, or the like,can be employed. Of those, in view of easiness of wire bonding, acircular shape or a shape similar to a circular shape is preferable. Thesize of the first connecting portion and the second connecting portioncan be adjusted appropriately based on the size of the light emittingelement, the arrangement of the electrodes, and the like, and their planview shapes can be circular shapes having a diameter of about 70 to 150μm respectively, for example. The first connecting portion and thesecond connecting portion may have different shapes and sizes, or thesame shape and size.

The first electrode has a first extending portion and a second extendingportion.

The second electrode has a third extending portion, and may optionallyhave a fourth extending portion.

There are no particular restrictions on the shapes or numbers of thefirst extending portion, the second extending portion, the thirdextending portion and the fourth extending portion, and they can be setat appropriate shapes and numbers.

In one embodiment, the first electrode preferably has the firstextending portion that extends linearly from the first connectingportion toward the second connecting portion, and the two secondextending portions that extend on two sides of (i.e., flanking) thefirst extending portion. The two second extending portions preferablyextend on two sides of the first extending portion and parallel to thefirst extending portion.

The second electrode preferably has two third extending portions thatextend parallel to the first extending portion between the firstextending portion and the two second extending portions. The secondelectrode preferably has two fourth extending portions. The two fourthextending portions preferably extend on the outside of the thirdextending portions, and more preferably extend parallel to the firstextending portion on the outside of the second extending portions.

The first extending portion and the second extending portions are linkedto the first connecting portion, and the third extending portions andthe optional fourth extending portions are linked to the secondconnecting portion. The first extending portion, the second extendingportions, the third extending portions, and the optional fourthextending portions serve as auxiliary electrodes for uniformly diffusingthe current supplied to the first connecting portion and secondconnecting portion to the semiconductor layers.

The first extending portion and the second extending portions preferablyextend from the first connecting portion. The distal ends of these arepreferably located more to the second connecting portion side than aline passing through the center point of another side and perpendicularto the first center line (this will sometimes be called the secondcenter line).

In particular, as discussed above, in the case where the firstconnecting portion is disposed near one end of the first center line, itis preferable for the first extending portion to extend over the firstcenter line.

The second extending portions preferably extend in a direction away fromthe first extending portion, then gradually or suddenly change directionand extend in a direction parallel to the first extending portion.Examples of a “direction away from the first extending portion” includea direction perpendicular to a direction parallel to the first extendingportion, and a direction that the two second extending portions draws anarc or a parabola having its center in the side of the second connectingportion.

The third extending portions and fourth extending portions preferablyextend from the second connecting portion. The distal ends of these arepreferably located more to the first connecting portion side than a linepassing through the center point of another side and perpendicular tothe first center line (the second center line). In particular, thefourth extending portions preferably extend farther than the firstconnecting portion in a direction away from the second connectingportion.

The two third extending portions preferably extend so as to form asingle U shape. This is because the distance is shorter than in the casewhere the bended shape is such that straight lines are linked up, thelength of the extending portions can be shorter, and thus less blockageand absorption of light by the extending portions.

The two fourth extending portions preferably extend in a direction awayfrom the third extending portions, then gradually or suddenly changedirection and extend in a direction parallel to the first extendingportion. Examples of a “direction away from the third extendingportions” include a direction perpendicular to a direction parallel tothe first extending portion, and a direction that draws an arc or aparabola having its center in the first connecting portion directionwith the two fourth extending portions.

The second extending portions, the third extending portions, and thefourth extending portions all may be bent at their distal ends. “Bent attheir distal ends” encompasses when the extending portions bend, andwhen they curve. The distal ends of the second extending portions, thethird extending portions, and the fourth extending portions may bendtoward the first connecting portion and/or the second connectingportion, or they may bend toward the inside of the semiconductor stackand/or the first center line of the semiconductor stack.

There are no particular restrictions on the width of the first extendingportion, the second extending portions, the third extending portions,and the fourth extending portions, but it is preferable, for example,for the width to be about 5 to 30%, about 5 to 20%, or about 5 to 15% ofthe diameter or the maximum length of the first connecting portion andthe second connecting portion. The widths of these extending portionsmay be different from one another, or may be the same. For instance, thefirst extending portion and the second extending portions preferablyhave the same width, and the third extending portions and the fourthextending portions preferably have the same width. Preferably, the firstextending portion and the second extending portions, and the thirdextending portions and the fourth extending portions have mutuallydifferent widths. Also, the first extending portion, the secondextending portions, the third extending portions, and the fourthextending portions may each have a width that varies from place toplace, or the width may be constant.

In the case where the semiconductor stack is a square, there are noparticular restrictions on the size of the square in plan view, but oneside can be from 600 to 1200 μm. The size, length, width, and/or spacingof the first extending portion, the second extending portions, the thirdextending portions, and the fourth extending portions can be suitablyadjusted according to the size of the semiconductor stack in plan view.

For example, in plan view, if the semiconductor stack measures 800 μmsquare, and the first connecting portion and the second connectingportion have a substantially circular shape with a diameter of about 100μm, the first connecting portion and the second connecting portion canbe separated by 420 to 660 μm. The overall length of the first extendingportion can be suitably adjusted within a range of 190 to 370 μm, theoverall length of the second extending portion can be suitably adjustedwithin a range of 750 to 1500 μm, the overall length of the thirdextending portion can be suitably adjusted within a range of 600 to 1100μm, and the overall length of the fourth extending portion can besuitably adjusted within a range of 1300 to 2200 μm. The distances f andm between the distal ends of the third extending portions and the secondextending portions in the direction in which the third extendingportions are extended parallel to the first extending portion can besuitably adjusted within a range of 120 to 190 μm, the distances g and jbetween the distal ends of the second extending portions and the fourthextending portions in the direction in which the second extendingportions are extended parallel to the first extending portion can besuitably adjusted within a range of 90 to 190 μm, and the distances hand k between the distal end of the first extending portion and thesecond connecting portion can be suitably adjusted within a range of 120to 170 μm. The widths of the first extending portion, the secondextending portions, the third extending portions, and the fourthextending portions can be within a range of about 2 to 15 μm.

In the case where the plan view shape of the semiconductor stack isrectangular, the first extending portion is preferably parallel to oneside of the semiconductor stack. Similarly, each of the second extendingportions, the third extending portions, and the fourth extendingportions preferably has a part that is parallel to one side of thesemiconductor stack. Such a layout of the extending portions allows thecurrent supplied from the first connecting portion and second connectingportion to be uniformly diffused over the entire face of thesemiconductor stack.

As shown in FIGS. 1A and 2A, the distances (b and b′) between the secondextending portions and the third extending portions are preferablyshorter than the distances (a and a′) between the first extendingportion and the third extending portions. That is, the distances betweenthe two second extending portions and the respectively adjacent twothird extending portions in a direction perpendicular to the firstextending portion are preferably shorter than the distances between thefirst extending portion and the adjacent two third extending portions.

The distances (a+b and a′+b′) between the first extending portion andthe two second extending portions are preferably equal.

The distances (a and a′) between the first extending portion and the twothird extending portions are preferably equal.

As shown in FIG. 1A, in the case where the light emitting element hasfourth extending portions, the distances (c and c′) between portions ofthe fourth extending portions extending parallel to the first extendingportion and portions of the second extending portions extending parallelto the first extending portion in a direction perpendicular to the firstextending portion are preferably shorter than the distances (b and b′)between the second extending portions and the third extending portions,and the distances (c and c′) are preferably shorter than the distances(a and a′) between the first extending portion and the third extendingportions.

Current tends to accumulate (electricity tends to flow) at the straightportion connecting the first connecting portion and second connectingportion. Accordingly, current tends to be diffused to the firstextending portion and the two third extending portions near the straightportion connecting the first connecting portion and second connectingportion. Therefore, the accumulation of current can be suppressed bywidening the spacing between the first extending portion and the thirdextending portions. On the other hand, at the area farther from thefirst connecting portion and the second connecting portion, that is, atthe area the closer to the periphery of the semiconductor stack, theless the current tends to diffuse. Therefore, at the extending portionsdisposed around the periphery of the semiconductor stack, currentdiffusion is promoted more by narrowing the spacing between the adjacentextending portions. That is, the order, starting from the spacing withthe greatest distance, is preferably the distance (a and a′) between thefirst extending portion and the third extending portions, the distance(b and b′) between the second extending portions and the third extendingportions, and the distance (c and c′) between the fourth extendingportions and the second extending portions. Disposing the extendingportions in this way reduces unevenness in the current densitydistribution of the semiconductor stack.

The a and a′ distances between the first extending portion and the twothird extending portions may be different from one another. Also, in adirection perpendicular to the first extending portion, the b and b′distances between the adjacent second extending portions and thirdextending portions may be different from one another. Furthermore, in adirection perpendicular to the first extending portion, the c and c′distances between the adjacent fourth extending portions and secondextending portions may be different from one another.

As shown in FIG. TA, in the case where the distal ends of the fourthextending portions are bent, the distance (e and e′) between the distalends of the fourth extending portions and the second extending portionsin the extending direction of the first extending portion is preferablylonger than the distance (c and c′) between portions of the fourthextending portions extending parallel to the first extending portion andportions of the second extending portions extending parallel to thefirst extending portion in a direction perpendicular to the firstextending portion.

This lessens the tendency for current to accumulate between the firstconnecting portion and the distal ends of the fourth extending portions,and allows the current to be uniformly diffused over the entire face ofthe semiconductor stack.

The e and e′ distances between the distal ends of the fourth extendingportions and the second extending portions in the extending direction ofthe first extending portion may be different from one another.

As shown in FIG. 2A, in the case where the distal ends of the secondextending portions are bent, the distance (d and d′) between the distalends of the second extending portions and the third extending portionsin the extending direction of the first extending portion is preferablylonger than the distances (b and b′) between portions of the secondextending portions extending parallel to the first extending portion andportions of the third extending portions extending parallel to the firstextending portion in a direction perpendicular to the first extendingportion.

This lessens the tendency for current to accumulate between the secondconnecting portion and the distal ends of the second extending portions,and allows the current to be uniformly diffused over the entire face ofthe semiconductor stack.

The d and d′ distances between the distal ends of the second extendingportions and the third extending portions in the extending direction ofthe first extending portion may be different from one another.

The first electrode and second electrode are preferably such that alight-transmissive conductive layer that covers substantially the entiresurface of the first conductivity type semiconductor layer or the secondconductivity type semiconductor layer is further disposed between theelectrodes and the semiconductor stack, as discussed below. Thelight-transmissive conductive layer may be provided on both the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer. The term “substantially the entire surface” heremeans a surface area of at least 90% or about 95% of the total surfacearea of the second conductivity type semiconductor layer. When thelight-transmissive conductive layer is formed, an insulating film may beformed under the first electrode or the second electrode, and in atleast part between the light-transmissive conductive layer and the firstconductivity type semiconductor layer or the second conductivity typesemiconductor layer. This insulating film makes it less likely thatlight will hit the first electrode and the second electrode and beabsorbed.

The first electrode and the second electrode are generally arranged suchthat a planar dimension of a rectangular shape enclosing the outer edgeof the first electrode or the second electrode, is preferably 60 to 90%,more preferably 70 to 90% with respect to the planar dimension of thelight-transmissive conductive layer or the semiconductor stack to bedescribed below. With this arrangement, electric current can be supplieduniformly on approximately the entire surface of the semiconductorstack. In addition, the planar dimension of the electrodes (the firstelectrode and the second electrode) occupying the upper surface of thesemiconductor stack can be reduced, so that absorption of light by theelectrodes can be reduced, thus, deterioration in the light extractionefficiency can be reduced.

Particularly, the rectangular shape enclosing the outer edge of thefirst electrode or the second electrode is preferably a similar shape oran approximately similar shape as the external shape of the lightemitting element or the external shape of the second conductivity typesemiconductor layer, with a size scaling down toward the gravity pointof the light emitting element. With the shape as described above, moreuniform supply of electric current can be realized. “Rectangular shapeenclosing the outer edge of the first electrode and the secondelectrode” refers to a rectangular shape which is in contact with theend portions arranged outermost side of the first electrode and thesecond electrode, and is enclosed by lines substantially parallel withthe periphery of the light emitting element or the second conductivitytype semiconductor layer. Also, in the specification, with“approximately similar shape”, variation in scale reduction of one ormore sides with respect to other sides of about 10% is permissible.

For the first electrode and the second electrode, for example, asingle-layer or a multi-layer of metal or alloy of Ni, Rh, Cr, Au, W,Pt, Ti, Al, etc., can be used, and of those, a multi-layer of Ti/Pt/Au,Ti/Rh/Au, or the like, respectively stacked in this order is preferablyused.

In one embodiment, the first electrode has a first connecting portionthat is provided near one end of a center line, and a plurality ofextending portions (namely, a first extending portion and secondextending portions) having parts that extend parallel to the centerline. The second electrode has a second connecting portion that isprovided on the other side of the center line where the first connectingportion is located, and a plurality of extending portions (namely, thirdextending portions and, optionally, fourth extending portions) havingparts that extend parallel to the center line. The first extendingportion, the second extending portions, the third extending portions,and the optional fourth extending portions are disposed alternately inanother center line direction that is perpendicular to the center line.The distance between the adjacent first extending portion, secondextending portions, third extending portions, and optional fourthextending portions decreases toward the side closer to the outerperiphery of the semiconductor stack.

(Conductive Layer)

The conductive layer disposed between the first electrode or the secondelectrode and the semiconductor stack is for supplying the electriccurrent supplied from the first electrode or the second electrodeuniformly into the entire surface of the semiconductor stack. A metalthin layer can be used for the conductive layer, but as the conductivelayer is disposed at the light extracting surface-side of the lightemitting element, a light-transmissive conductive layer, morespecifically, a conductive oxide layer is preferably used. Examples ofthe conductive oxide include an oxide containing at least one selectedfrom the group having of Zn, In, Sn, and Mg, and more specifically, ZnO,In₂O₃, SnO₂, ITO (Indium Tin Oxide; ITO), IZO (Indium Zinc Oxide), GZO(Gallium doped Zinc Oxide) and the like. The conductive oxide (inparticular, ITO) is a material which exhibits high light transmissivity(for example, 60% or greater, 70% or greater, 75% or greater, or 80% orgreater) to visible light (in the visible light region) and has arelatively high electric conductivity, so that can be used preferably.

(Packaging)

The light emitting element can be mounted on a base member and enclosedwith a sealing member to constitute a light emitting device. The lightemitting element can be mounted either in a face-up manner or in aface-down manner.

The base member is generally constituted with a wiring and an insulatingmaterial. The wiring is used to supply electric power to the electrodeof the light emitting element. For this purpose, any electricallyconductive materials which can serve this function can be used. As forsuch materials, appropriate materials can be selected from materialsdescribed above used for the first electrode etc. Examples of theinsulating materials include ceramics, resins, dielectric materials,pulps, glass or composite materials of those, or complex materials ofthose materials and conductive materials (for example, metal, carbon,etc).

The wiring and the insulating material may be formed integrally in anapproximately rectangular parallelepiped shape or an approximatelycuboid shape, and a recess may be formed in any portion for mounting thelight emitting element.

The sealing member is used to protect the light emitting element and theconnecting members such as a wire from external environment, and anymaterials which allow efficient extraction of light from the lightemitting element can be employed for the sealing member. For example, alight transmissive resin can be employed. The light transmissive resincan contain fluorescent materials, light diffusion materials, fillersand the like.

The light transmissive resin allows penetration of light, which is 60%or greater of light emitted from the light emitting layer, and furtherpreferably allows penetration of 70% or greater, 80% or greater, or 90%or greater of light emitted from the light emitting layer. Examples ofsuch resin include a silicone resin, an epoxy resin, and the like.

The fluorescent materials known in the art may be employed. For example,in the case where a gallium nitride based light emitting element to emitblue light is used as the light emitting element, fluorescent materialsto absorb blue light, such as a YAG-based fluorescent material or aLAG-based fluorescent material to emit yellow to green light, aSiAlON-based fluorescent material (β-sialon-based fluorescent material)to emit green light, and a SCASN-based fluorescent material and aCASN-based fluorescent material to emit red light, can be used singly orin combination. Further, fluoride fluorescent materials, whoseexcitation band is in blue region and which is red light emittingfluorescent materials having narrow half bandwidth of the emission peak,such as K₂SiF₆:Mn⁴⁺, K₂TiF₆:Mn⁴⁺, K₂SnF₆:Mn⁴⁺, Na₂TiF₆:Mn⁴⁺,Na₂ZrF₆:Mn⁴⁺, K₂Si_(0.5)Ge_(0.5)F₆:Mn⁴⁺.

Examples of the light emitting element of the present disclosure willnow be described in detail through reference to the drawings.

Example 1

As shown in FIGS. 1A and 1C, the light emitting element 10A in Example 1has a substrate 2, a semiconductor stack 5 having an n-typesemiconductor layer 3 (a first conductivity type semiconductor layer),an active layer 33, and a p-type semiconductor layer 4 (a secondconductivity type semiconductor layer) provided in that order over thesubstrate 2, an n-side electrode (a first electrode 6) formed on then-type semiconductor layer 3, and a p-side electrode (a second electrode7) that is disposed on the p-type semiconductor layer 4 and surroundingthe n-side electrode.

The substrate 2 and the semiconductor stack 5 (in particular, the p-typesemiconductor layer 4) has an approximately square shape in a plan view,the length of a side of the semiconductor stack 5 or the substrate 2 is800 μm.

The first electrode 6 (the n-side electrode) is formed on the n-typesemiconductor layer 3 at the part of the semiconductor stack 5 exposedby removing part of the p-type semiconductor layer 4 and the activelayer 33, and is electrically connected to the n-type semiconductorlayer 3. The first electrode 6 (the n-side electrode) is surrounded bythe p-type semiconductor layer 4 and the active layer 33.

The second electrode 7 (the p-side electrode) is formed on the p-typesemiconductor layer 4. Alight-transmissive conductive layer 8, which isformed over substantially the entire surface of the p-type semiconductorlayer 4, is disposed between the p-type semiconductor layer 4 and thesecond electrode 7 (the p-side electrode). The second electrode 7 (thep-side electrode) is electrically connected to the p-type semiconductorlayer 4 via the conductive layer 8.

The semiconductor stack 5, the n-side electrode, and the p-sideelectrode are covered by a protective film 9, except at a part of afirst connecting portion 6 a and a part of a second connecting portion 7a (discussed below).

The first electrode 6 (the n-side electrode) and the second electrode 7(the p-side electrode) respectively have the first connecting portion 6a and the second connecting portion 7 a, which are electricallyconnected to an external circuit. The first connecting portion 6 a andthe second connecting portion 7 a are disposed near the respective endsof a first center line of the semiconductor stack 5. This first centerline is parallel to one side of the semiconductor stack 5 in the planview, and passes through the center point of another edge that isperpendicular to this first edge. The first connecting portion 6 a andthe second connecting portion 7 a are substantially circular, with adiameter of about 100 μm. The distance between the first connectingportion 6 a and the second connecting portion 7 a (between centerpoints) is 473 μm.

The first electrode 6 (the n-side electrode) has a first extendingportion 6 b that extends in a straight line from the first connectingportion 6 a toward the second connecting portion 7 a, and two secondextending portions 6 c that extend from the first connecting portion 6 aparallel to the first extending portion 6 b on two sides of (flanking)the first extending portion 6 b. The first extending portion 6 b extendsover the first center line and parallel to one side of the semiconductorstack 5.

The first extending portion 6 b and the second extending portions 6 chave substantially the same width, which is 12 μm. The total length ofthe first extending portion 6 b is 215 μm. The total length of thesecond extending portions 6 c is 1100 μm, and the straight line part ofthe second extending portions 6 c parallel to the first extendingportion 6 b is about 470 μm.

The second electrode 7 (the p-side electrode) has two third extendingportions 7 b that extend parallel to the first extending portion 6 b, inbetween the first extending portion 6 b and the two second extendingportions 6 c. Also, the second connecting portion 7 a further has fourthextending portions 7 c that extend parallel to the first extendingportion 6 b, on the outside of the second extending portions 6 c. Thedistal ends 7 d of these fourth extending portions 7 c are bent towardthe first connecting portion 6 a.

The width of the third extending portions 7 b is 8 μm. The width of thefourth extending portions 7 c decreases as distance from the secondconnecting portion increases, and is 10 μm at one part and 6 μm atanother. The total length of the third extending portions 7 b is 666 μm,and the straight line part of the third extending portions parallel tothe first extending portion 6 b is about 235 μm. The total length of thefourth extending portions 7 c is 1940 μm, and the straight line part ofthe fourth extending portions parallel to the first extending portion 6b is about 760 μm.

The distances a and a′ between the first extending portion 6 b and thetwo third extending portions 7 b are the same, at 130 μm. The distance fbetween the distal ends of the third extending portions 7 b and thesecond extending portions 6 c in the direction in which the thirdextending portions 7 b are extended parallel to the first extendingportion 6 b is 166 μm.

The distances b and b′ between the third extending portions 7 b and thesecond extending portions 6 c are the same, at 102 μm.

The distances c and c′ between the second extending portions 6 c and thefourth extending portions 7 c are the same, at 60 μm.

The distances e and e′ between the distal ends 7 d of the fourthextending portions 7 c and the second extending portions 6 c are thesame, at 91 μm.

The distances g between the distal ends of the second extending portions6 c and the fourth extending portions 7 c in the direction in which thesecond extending portions 6 c are extended parallel to the firstextending portion 6 b is 104 μm. The distance h between the distal endof the first extending portion 6 b and the second connecting portion 7 ais 152 μm.

Therefore, the distances b and b′ between the second extending portions6 c and the third extending portions 7 b are shorter than the distancesa and a′ between the first extending portion 6 b and the third extendingportions 7 b.

The distances c and c′ between portions of the fourth extending portionsextending parallel to the first extending portion and portions of thesecond extending portions extending parallel to the first extendingportion in a direction perpendicular to the first extending portion areshorter than the distances b and b′ between the second extendingportions 6 c and the third extending portions 7 b.

The distances c and c′ are shorter than the distances a and a′ betweenthe first extending portion 6 b and the two third extending portions 7b.

The distances c and c′ are shorter than the distances e and e′ betweenthe distal ends 7 d of the fourth extending portions 7 c and the secondextending portions 6 c.

In the light emitting element 10A, the second electrode 7 which is ap-side electrode surrounding the first electrode 6 which is an n-sideelectrode is arranged in a region with a scale of about 70% with respectto the planar dimension of the conductive layer 8 centered at the centerof the semiconductor stack 5. In other words, when assuming fourstraight lines which are respectively in contact with the end portionsat outermost sides of the second electrode 7, and in parallel with thefour outer edges of the semiconductor stack 5, the planar dimensionsurrounded with the four straight lines has a scale ratio ofapproximately 70% with respect to the planar dimension of the conductivelayer 8 (see, an area enclosed by dotted line in FIG. 1A).

Modification Example 1 of Example 1

As shown in FIG. 1B, the light emitting element 10B of this ModificationExample 1 of Example 1 has substantially the same configuration as thelight emitting element 10A in Example 1, except that the first electrode16 is the p-side electrode, and the second electrode 17 is the n-sideelectrode.

That is, the light emitting element 10B has a first electrode 16 as thep-side electrode, which has a first connecting portion 16 a, a firstextending portion 16 b, and two second extending portions 16 c. The thelight emitting element 10B has a second electrode 17 as the n-sideelectrode, which has a second connecting portion 17 a, two thirdextending portions 17 b, and two fourth extending portions 17 c. Thedistal ends 17 d of these fourth extending portions 17 c are bent towardthe first connecting portion 16 a.

The width of the first extending portion 16 b is 12 μm.

The width of the second extending portion 16 c is 12 μm.

The width of the third extending portion 17 b is 8 μm.

The width of the fourth extending portions 17 c is 10 μm at a place nearthe second connecting portion 17 a, and 6 μm at the distal end side.

Modification Example 2 of Example 1

As shown in FIG. 1D, the light emitting element 10C of this ModificationExample 2 of Example 1 is similar to the light emitting element 10A inthat the second connecting portion 7 a, the third extending portions 7b, and the fourth extending portions 7 c are disposed at the secondelectrode 7, and has substantially the same configuration as the lightemitting element 10A in Example 1 except that the distal ends of thefourth extending portions 7 c are not bent, and extend linearly towardthe end of the light emitting element 10C, past the outermost end of thefirst connecting portion 6 a.

The distance between the distal ends of the fourth extending portions 7c near the end of the light emitting element and the end of thesemiconductor stack 5 in the direction in which the fourth extendingportions 7 c extend parallel to the first extending portion 6 b is 62μm.

Example 2

As shown in FIG. 2A, the light emitting element 20A in this Example 2has a substrate 2, a semiconductor stack 5 having an n-typesemiconductor layer 3 (a first conductivity type semiconductor layer),an active layer 33, and a p-type semiconductor layer 4 (a secondconductivity type semiconductor layer) provided in that order over thesubstrate 2, an n-side electrode (a second electrode 27) formed on then-type semiconductor layer 3, and an p-side electrode (a first electrode26) that is disposed on the p-type semiconductor layer 4 and surroundingthe n-side electrode (the second electrode 27).

The substrate 2 and the semiconductor stack 5 (in particular, the p-typesemiconductor layer 4) have an approximately square shape in a planview. For example, the length of a side of the semiconductor stack 5 orthe substrate 2 is 800 μm.

The second electrode 27 (the n-side electrode) is formed on the n-typesemiconductor layer 3 at the part of the semiconductor stack 5 exposedby removing part of the p-type semiconductor layer 4 and the activelayer 33, and is electrically connected to the n-type semiconductorlayer 3. The second electrode 27 (the n-side electrode) is surrounded bythe p-type semiconductor layer 4 and the active layer 33.

The first electrode 26 (the p-side electrode) is formed on the p-typesemiconductor layer 4. Alight-transmissive conductive layer 28, which isformed over substantially the entire surface of the p-type semiconductorlayer 4, is disposed between the p-type semiconductor layer 4 and thefirst electrode 26 (the p-side electrode). The first electrode 26 (thep-side electrode) is electrically connected to the p-type semiconductorlayer 4 via the conductive layer 28.

The semiconductor stack 5, the n-side electrode, and the p-sideelectrode are covered by a protective film 9, except at a part of afirst connecting portion 26 a and a part of a second connecting portion27 a (discussed below).

The first electrode 26 (the p-side electrode) and the second electrode27 (the n-side electrode) respectively have the first connecting portion26 a and the second connecting portion 27 a. The first connectingportion 26 a and the second connecting portion 27 a are disposed nearthe respective ends of a first center line of the semiconductor stack 5.

The first electrode 26 (the p-side electrode) has a first extendingportion 26 b that extends in a straight line from the first connectingportion 26 a toward the second connecting portion 27 a, and two secondextending portions 26 c that extend from the first connecting portion 26a parallel to the first extending portion 26 b on two sides of(flanking) the first extending portion 26 b. The first extending portion26 b extends over the first center line and parallel to one side of thesemiconductor stack 5. The first extending portion has the width of 12μm. The width of the second extending portions 26 c decreases movingaway from the first connecting portion 26 a, and is 10 μm at one partand 6 μm at another. The total length of the first extending portion 26b is 248 μm. The total length of the second extending portions 26 c is1760 μm, and the straight line part parallel to the first extendingportion 26 b is about 880 μm.

The distal ends 26 d of these second extending portions 26 c are benttoward the second connecting portion 27 a.

The second electrode 27 (the n-side electrode) has two third extendingportions 27 b that extend parallel to the first extending portion 26 b,in between the first extending portion 26 b and the two second extendingportions 26 c. The third extending portions 27 b have distal ends 27 cwhich are bent toward the first connecting portion 26 a.

The width of the the third extending portions 27 b is 8 μm. The totallength of the third extending portion 27 b is 666 μm, and the straightline part parallel to the first extending portion 26 b is about 324 μm.

The distances a and a′ between the first extending portion 26 b and thetwo third extending portions 27 b are the same, at 130 μm.

The distances b and b′ between the third extending portion 27 b and thesecond extending portion 26 c are the same, at 61.5 μm.

The distances d and d′ between the distal ends 26 d of the secondextending portions 26 c and the third extending portions 27 b are thesame, at 112 μm.

In this light emitting element 20A, the first electrode 26 surroundingthe the second electrode 27 is arranged in a region with a scalereduction of about 70% with respect to the planar dimension of theconductive layer 28 centered at the center of the semiconductor stack 5.

The light emitting element in this Example has substantially the sameconfiguration as the light emitting element in Example 1 except for theabove.

Modification Example 1 of Example 2

As shown in FIG. 2B, the light emitting element 20B of this ModificationExample 1 of Example 2 has substantially the same configuration as thelight emitting element 20A in Example 2, except that the secondelectrode 227 is the p-side electrode, and the first electrode 226 isthe n-side electrode.

That is, the light emitting element 20B has a first electrode 226 as then-side electrode which has a first connecting portion 226 a, a firstextending portion 226 b, and two second extending portions 226 c. Thedistal ends 226 d of these second extending portions 226 c are benttoward the second connecting portion 227 a. The light emitting element20B has a second electrode 227 as the p-side electrode, which has asecond connecting portion 227 a, and two third extending portions 227 b.The distal ends 227 c of these third extending portions 227 b are benttoward the first connecting portion 226 a.

The width of the first extending portion 226 b is 10 μm.

The width of the second extending portion 226 c decreases moving awayfrom the first connecting portion 226 a, and is 10 μm at one part and 6μm at another.

The width of the third extending portion 227 b is 8 μm.

Example 3

As shown in FIG. 3 , the light emitting element 30 in this Example 3 hassubstantially the same configuration as the light emitting element 10Ain Example 1, except that a first connecting portion 36 a of the n-sideelectrode (the first electrode) is moved in the direction toward asecond connecting portion 37 a of the p-side electrode (the secondelectrode), which is accompanied by a slight change in how a firstextending portion 36 b and second extending portions 36 c extend fromthe first connecting portion 36 a.

Example 4

As shown in FIG. 4 , the light emitting element 40 in this Example 4 hassubstantially the same configuration as the light emitting element 10Ain Example 1, except that a first connecting portion 46 a of the n-sideelectrode is moved in the direction toward the opposite side from asecond connecting portion 47 a of the p-side electrode, which isaccompanied by a slight change in how a first extending portion 46 b andsecond extending portions 46 c extend from the first connecting portion46 a.

Example 5

As shown in FIG. 5 , the light emitting element 50 in this Example 5 issuch that a first connecting portion 56 a (the n-side electrode) ismoved so as to come into contact with the nearest side of thesemiconductor stack 5 in the plan view. Consequently, the distancebetween the first connecting portion 56 a and a second connectingportion 57 a is extended from the 473 μm of Example 1 to 593 μm.

The length of the first extending portion 56 b and the second extendingportions 56 c is increased so that the distance between the secondconnecting portion 57 a and the distal end of the first extendingportion 56 b, and the distance between the distal end of the secondextending portions 56 c and the fourth extending portions 57 c in thedirection in which the second extending portions 56 c extend parallel tothe first extending portion 56 b will be the same as the distancebetween these members in the light emitting element 10A. In particular,the total length of the first extending portion 56 b is 335 μm, and thetotal length of the second extending portions 56 c is 1300 μm.

Also, the length of the third extending portions 57 b and the fourthextending portions 57 c are extended toward the one side of thesemiconductor stack 5 where the first connection portion 56 a comes intocontact. In particular, the total length of the third extending portions57 b is 978 μm, and the total length of the fourth extending portions 57c is 1612 μm. The distance between the distal ends of the thirdextending portions 57 b and the second extending portions 56 c touchingone edge of the semiconductor stack 5 is 174 μm. The distance betweenthe distal ends of the fourth extending portions 57 c and one edge ofthe semiconductor stack 5 is 62 μm.

Example 6

As shown in FIG. 6 , the light emitting element 60 in this Example 6 issuch that a first connecting portion 66 a (the n-side electrode) ismoved so as to come into contact with the nearest side of thesemiconductor stack 5 in the plan view. Consequently, the distancebetween the first connecting portion 66 a and a second connectingportion 67 a is extended from the 473 μm of Example 1 to 593 μm.

The length of the first extending portion 66 b and the second extendingportions 66 c is increased so that the distance between the secondconnecting portion 67 a and the distal end of the first extendingportion 66 b, and the distance between the distal end of the secondextending portions 66 c and the fourth extending portions 67 c in thedirection in which the second extending portions 66 c extend parallel tothe first extending portion 66 b will be the same as the distancebetween these members in the light emitting element 10A. In particular,the total length of the first extending portion 66 b is 335 μm, and thetotal length of the second extending portions 66 c is 1300 μm,

Also, the length of the third extending portions 67 b and the fourthextending portions 67 c are extended to the one edge side of thesemiconductor stack 5 where the first extending connection portion 66 acomes into contact. In particular, the total length of the thirdextending portions 67 b is 978 μm, and the total length of the fourthextending portions 67 c is 1486 μm. The distance between the distal endsof the third extending portions 67 b and the second extending portions66 c touching one edge of the semiconductor stack 5 is 174 μm. Thedistance between the distal ends of the fourth extending portions 67 cand one edge of the semiconductor stack 5 is 125 μm.

Example 7

As shown in FIG. 7 , the light emitting element 70 in this Example 7 hassubstantially the same configuration as the light emitting element 10Ain Example 1, except that the total length of the second extendingportions 76 c is shorter (total length: 832 μm), the distance betweenthe distal ends of the second extending portions 76 c and the fourthextending portions 77 c in the direction in which the second extendingportions 76 c extend parallel to the first extending portion 76 b islonger (distance j: 172 μm), the first extending portion 76 b is longer,and the distance between the first extending portion 76 b and the secondconnecting portion 77 a is shorter (distance k: 136 μm).

Example 8

As shown in FIG. 8 , the light emitting element 80 in this Example 8 hassubstantially the same configuration as the light emitting element 10Ain Example 1, except that the total length of the third extendingportions 87 b is longer (total length: 760 μm), the distance between thedistal ends of the third extending portions 87 b and the secondextending portions 86 c in the direction in which the third extendingportions 87 b extend parallel to the first extending portion 86 b isshorter (distance j: 130 μm).

Example 9

As shown in FIG. 9 , the light emitting element 90 in this Example 9 hassubstantially the same configuration as the light emitting element 10Ain Example 1, except that the total length of the second extendingportions 96 c is shorter (total length: 832 μm), the distance betweenthe distal ends of the second extending portions 96 c and the fourthextending portions 97 c in the direction in which the second extendingportions 96 c extend parallel to the first extending portion 96 b islonger (distance j: 172 μm), the first extending portion 96 b is longer,the distance between the first extending portion 96 b and the secondconnecting portion 97 a is shorter (distance k: 136 μm), the totallength of the third extending portions 97 b is longer (total length: 760μm), and the distance between the distal ends of the third extendingportions 97 b and the second extending portions 96 c in the direction inwhich the third extending portions 97 b extend parallel to the firstextending portion 96 b is shorter (distance m: 130 μm).

Reference Example

As shown in FIG. 10 , the light emitting element 100 in this referenceexample has substantially the same configuration as in Example 1, exceptthat the distance X between the second extending portions 106 c and thethird extending portions 107 b is equal to the distance Y between thefirst extending portion 106 b and the third extending portions 107 b,and the distance Z between the second extending portions 106 c and thefourth extending portions 107 c. X=Y=Z=99 μm.

Evaluation of Light Emitting Elements

The distribution of current density in the light emitting elements 10A,50, 80 of Examples 1, 5, 8 and the light emitting element 100 ofReference Example was analyzed by using simulation software based on thefinite element method. The results are shown in FIG. 11 . In FIG. 11 ,darker shading indicates a higher current density.

With the light emitting element 100, since the distance between thefirst extending portion and the third extending portions is short,current concentrates between the first connecting portion and secondconnecting portion, and current tends to accumulate in the center. Incontrast, with the light emitting elements 10A, 50, and 80, in which thedistance between the first extending portion and the third extendingportions is increased, there is less concentration of current in thecenter portion. Also, current is diffused up to the periphery of thesemiconductor stack by shortening the distance between the secondextending portions and the fourth extending portions, and the distancebetween the third extending portions and the second extending portionsin a direction perpendicular to the first extending portion, as distancefrom the first connecting portion and the second connecting portionincreases (that is, as the distance from the periphery of thesemiconductor stack decreases).

As to the light emitting element 80, the third extending portions arelonger than that of the light emitting element 10A, and the distal endsof the third extending portions are closer to the first connectingportion than that of the light emitting element 10A, so current isdiffused more in the center portion of the light emitting element 80.

As to the light emitting element 50, because the first connectingportion is disposed around (on one side of) the semiconductor stack, andthe distal ends of the fourth extending portions extend to near thecorners of the semiconductor stack, it can be seen that current spreadsout in the corners of the semiconductor stack as well.

Similar effect is obtained in current density distribution with thelight emitting elements 20A, 30, 40, 60, 70, and 90 in the otherExamples.

Three each of the light emitting elements of the above-mentionedExamples 1, 3, 4, 5, 6 and 8 (that is, the light emitting elements 10A,30, 40, 50, 60, and 80) were prepared, and the light emitting element100 of the Reference Example was similarly prepared. These lightemitting elements were evaluated as follows.

The light emitting elements 10A, 30, 40, 50, and 60 was checked for theeffect of distance between the first connecting portion of the n-sideelectrode (the first electrode) and the second connecting portion of thep-side electrode (the second electrode). Current of 350 mA was appliedto each light emitting element, and the Po, Vf, and initial powerefficiency were compared, which revealed these to be better in the lightemitting elements 10A, 30, and 40 than in the light emitting elements 50and 60. Consequently, from the standpoint of Po, Vf, and initial powerefficiency, it is preferable for the first connecting portion and thesecond connecting portion to be provided somewhat closer together, andit can be seen that the first connecting portion of the n-side electrodeis preferably surrounded by the p-type semiconductor layer rather thanbeing in contact with the closest edge of the semiconductor stack.

A current of 350 mA was applied to the light emitting elements 10A and80 and the light emitting element 100 of the Reference Example, and theoutput power (Po) and the forward voltage (Vf) were measured. The outputpower is given in units of mW.

The initial power efficiency was found from the formula: {outputpower/(current×voltage)}×100 [%]. The current is in units of mA, and thevoltage is in units of V.

As to the initial power efficiency, the light emitting element 80 wasbetter than the light emitting element 10A and the light emittingelement 100. For Vf, the light emitting element 80 was better than thelight emitting element 10A, and the light emitting element 10A wasbetter than the light emitting element 100.

These effects lead to the conclusion that providing the first connectingportion and the second connecting portion somewhat close together iseffective at increasing the power output, and that increasing thedistances x and y over the distance z, and somewhat shortening thedistance m are effective at reducing the Vf and current accumulation.From the standpoint of initial power efficiency, the light emittingelement 80 was the best in that it struck a good balance between thesepoints.

Evaluation of Light Emitting Device

The light emitting element 80 of Example 8 and the light emittingelement 100 of the Reference Example were each mounted in a ceramicpackage having a cavity (3 mm long×3 mm wide×0.52 mm high), and thelight emitting element was sealed with a silicone resin containing YAGto produce a white light emitting device. These white light emittingdevices were measured for Vf, light flux (lm), and emission efficiency(lm/W), and then compared.

As a result, the white light emitting device in which the light emittingelement 80 was mounted was found to have a Vf that was 0.59% lower, alight flux that was 0.39% higher, and an emission efficiency that was0.93% higher than in the white light emitting device in which the lightemitting element 100 was mounted.

Consequently, with a white light emitting device, the current densitydistribution of the light emitting element 80, that is, the emissiondistribution, was improved over that of the light emitting device 100 inthe Reference Example, so the light flux and the emission efficiencywere believed to be improved.

INDUSTRIAL APPLICABILITY

A light emitting element according to the present disclosure can besuitably employed for various lighting apparatuses, in particular, alight source for lighting, an LED display, backlight source for a liquidcrystal display device, signals, a lighted switch, various sensors,various indicators, an auxiliary light source for moving image, otherconsumer light sources, or the like.

What is claimed is:
 1. A light emitting element comprising: asemiconductor structure; and first and second electrodes formed abovethe semiconductor structure, wherein: in a plan view: the firstelectrode consists of a first pad electrode configured to be bonded witha first conductive wire and electrically connected to a first externalelectrode or a first external terminal, and three extending portionsextending from the first pad electrode, the three extending portionsbeing a first extending portion, and exactly two second extendingportions, the second electrode consists of a second pad electrodeconfigured to be bonded with a second conductive wire and electricallyconnected to a second external electrode or a second external terminal,and two third extending portions extending from the second padelectrode, the first extending portion extends linearly in a directionfrom the first pad electrode toward the second pad electrode, each ofthe two second extending portions includes a bent portion, and a linearportion that extends in a direction substantially parallel to thedirection in which the first extending portion extends, each of the twothird extending portions includes a bent portion, and a linear portionthat extends in a direction substantially parallel to the direction inwhich the first extending portion extends and that is located betweenthe first extending portion and a respective one of the linear portionsof the two second extending portions, and along an imaginary line thatextends through the two second extending portions and the two thirdextending portions in a direction perpendicular to the direction inwhich the first extending portion extends, an entirety of the secondelectrode is located inward of the two second extending portions.
 2. Thelight emitting element according to claim 1, wherein: in the plan view,in directions parallel to the direction in which the first extendingportion extends, each of the second extending portions extends beyond aposition of the second pad electrode.
 3. The light emitting elementaccording to claim 1, wherein: in the plan view, each of the first padelectrode and the second pad electrode has a substantially circularshape.
 4. The light emitting element according to claim 1, wherein: inthe plan view, each of the first pad electrode and the second padelectrode has a polygonal shape.
 5. The light emitting element accordingto claim 1, wherein: in the plan view: a maximum dimension of the firstpad electrode is greater than widths of each of the first extendingportion and the second extending portions, and a maximum dimension ofthe second pad electrode is greater than widths of each of the thirdextending portions.
 6. The light emitting element according to claim 1,wherein: in the plan view: distances respectively between the firstextending portion and the second extending portions are the same, anddistances respectively between the first extending portion and the thirdextending portions are the same.
 7. The light emitting element accordingto claim 1, wherein: in the plan view, the two third extending portionsextend to form a U shape.
 8. The light emitting element according toclaim 1, wherein: in the plan view: each of the two second extendingportions further includes an additional bent portion, and in each of thetwo second extending portions, the linear portion respectively extendsfrom the bent portion to the additional bent portion.
 9. The lightemitting element according to claim 8, wherein: in the plan view, indirections parallel to the direction in which the first extendingportion extends, at least a portion of the additional bent portion ofeach of the second extending portions extends beyond a position of thesecond pad electrode.
 10. The light emitting element according to claim8, wherein: in the plan view, each of the two second extending portionsfurther includes an additional linear portion extending from theadditional bent portion in a direction perpendicular to the direction inwhich the first extending portion extends.
 11. The light emittingelement according to claim 1, wherein: the semiconductor structureincludes a first conductivity type semiconductor layer and a secondconductivity type semiconductor layer, and the first conductivity typesemiconductor layer is disposed over the second conductivity typesemiconductor layer.
 12. The light emitting element according to claim11, wherein: each of the first conductivity type semiconductor layer andthe second conductivity type semiconductor layer is made of a nitridesemiconductor material represented by a general formula In_(x)Al_(y)Ga_(1-x-y)N (0<x<1, 0<y<1, x+y<1).
 13. The light emitting elementaccording to claim 11, wherein: the first electrode is formed on thefirst conductivity type semiconductor layer, and the second electrode isformed on the second conductivity type semiconductor layer.
 14. Thelight emitting element according to claim 11, wherein: the firstconductivity type semiconductor layer is a p-type semiconductor layer,and in the plan view, the first electrode and the second electrode areentirely surrounded by the p-type semiconductor layer.
 15. The lightemitting element according to claim 1, wherein: in the plan view, thefirst extending portion extends from the first pad electrode to a distalend without branching.
 16. The light emitting element according to claim1, wherein: in the plan view, each of the two second extending portionsextends from the first pad electrode to a distal end without branching.17. The light emitting element according to claim 16, wherein: in theplan view, each of the two third extending portions extends from thesecond pad electrode to a distal end without branching.
 18. The lightemitting element according to claim 1, wherein: in the plan view, eachof the two third extending portions extends from the second padelectrode to a distal end without branching.
 19. The light emittingelement according to claim 1, wherein: in the plan view: the firstextending portion extends from the first pad electrode to a distal endwithout branching, each of the two second extending portions extendsfrom the first pad electrode to a distal end without branching, and eachof the two third extending portions extends from the second padelectrode to a distal end without branching.
 20. The light emittingelement according to claim 1, wherein: in the plan view, the secondelectrode is, as a whole, U-shaped.
 21. A light emitting elementcomprising: a semiconductor structure; and first and second electrodesformed above the semiconductor structure, wherein: in a plan view: thefirst electrode consists of a first pad electrode configured to bebonded with a first conductive wire and electrically connected to afirst external electrode or a first external terminal, and threeextending portions extending from the first pad electrode, the threeextending portions being a first extending portion, and exactly twosecond extending portions, the second electrode consists of a second padelectrode configured to be bonded with a second conductive wire andelectrically connected to a second external electrode or a secondexternal terminal, and four extending portions extending from the secondpad electrode, the four extending portions being exactly two thirdextending portions, and exactly two fourth extending portions, the firstextending portion extends linearly in a direction from the first padelectrode toward the second pad electrode, each of the two secondextending portions includes a bent portion, and a linear portion thatextends in a direction substantially parallel to the direction in whichthe first extending portion extends, each of the two third extendingportions includes a bent portion, and a linear portion that extends in adirection substantially parallel to the direction in which the firstextending portion extends and that is located between the firstextending portion and a respective one of the linear portions of the twosecond extending portions, each of the two fourth extending portionsincludes a bent portion, and a linear portion that extends in adirection substantially parallel to the direction in which the firstextending portion extends, and each of the two second extending portionsis located between a respective one of the linear portions of the twothird extending portions and a respective one of the linear portions ofthe two fourth extending portions.
 22. The light emitting elementaccording to claim 21, wherein: in the plan view, along an imaginaryline that extends through the two second extending portions, the twothird extending portions, and the two fourth extending portions in adirection perpendicular to the direction in which the first extendingportion extends, an entirety of the first electrode is located inward ofthe two fourth extending portions.
 23. The light emitting elementaccording to claim 21, wherein: in the plan view, in directions parallelto the direction in which the first extending portion extends, each ofthe fourth extending portions extends beyond a position of the first padelectrode.
 24. The light emitting element according to claim 21,wherein: in the plan view, each of the first pad electrode and thesecond pad electrode has a substantially circular shape.
 25. The lightemitting element according to claim 21, wherein: in the plan view, eachof the first pad electrode and the second pad electrode has a polygonalshape.
 26. The light emitting element according to claim 21, wherein: inthe plan view: a maximum dimension of the first pad electrode is greaterthan widths of each of the first extending portion and the secondextending portions, and a maximum dimension of the second pad electrodeis greater than widths of each of the third extending portions and thefourth extending portions.
 27. The light emitting element according toclaim 21, wherein: in the plan view: distances respectively between thefirst extending portion and the second extending portions are the same,distances respectively between the first extending portion and the thirdextending portions are the same, and distances respectively between thefirst extending portion and the fourth extending portions are the same.28. The light emitting element according to claim 21, wherein: in theplan view, the two third extending portions extend to form a U shape.29. The light emitting element according to claim 21, wherein: in theplan view: each of the two fourth extending portions further includes anadditional bent portion, and in each of the two fourth extendingportions, the linear portion respectively extends from the bent portionto the additional bent portion.
 30. The light emitting element accordingto claim 29, wherein: in the plan view, in directions parallel to thedirection in which the first extending portion extends, at least aportion of the additional bent portion of each of the fourth extendingportions extends beyond a position of the first pad electrode.
 31. Thelight emitting element according to claim 29, wherein: in the plan view,each of the two fourth extending portions further includes an additionallinear portion extending from the additional bent portion in a directionperpendicular to the direction in which the first extending portionextends.
 32. The light emitting element according to claim 21, wherein:the semiconductor structure includes a first conductivity typesemiconductor layer and a second conductivity type semiconductor layer,and the first conductivity type semiconductor layer is disposed over thesecond conductivity type semiconductor layer.
 33. The light emittingelement according to claim 32, wherein: each of the first conductivitytype semiconductor layer and the second conductivity type semiconductorlayer is made of a nitride semiconductor material represented by ageneral formula In_(x)Al_(y) Ga_(1-x-y)N (0<x<1, 0<y<1, x+y<1).
 34. Thelight emitting element according to claim 32, wherein: the firstelectrode is formed on the first conductivity type semiconductor layer,and the second electrode is formed on the second conductivity typesemiconductor layer.
 35. The light emitting element according to claim32, wherein: the first conductivity type semiconductor layer is a p-typesemiconductor layer, and in the plan view, the first electrode and thesecond electrode are entirely surrounded by the p-type semiconductorlayer.
 36. The light emitting element according to claim 21, wherein: inthe plan view, the first extending portion extends from the first padelectrode to a distal end without branching.
 37. The light emittingelement according to claim 21, wherein: in the plan view, each of thetwo second extending portions extends from the first pad electrode to adistal end without branching.
 38. The light emitting element accordingto claim 37, wherein: in the plan view, each of the two third extendingportions extends from the second pad electrode to a distal end withoutbranching.
 39. The light emitting element according to claim 38,wherein: in the plan view, each of the two fourth extending portionsextends from the second pad electrode to a distal end without branching.40. The light emitting element according to claim 21, wherein: in theplan view, each of the two third extending portions extends from thesecond pad electrode to a distal end without branching.
 41. The lightemitting element according to claim 21, wherein: in the plan view, eachof the two fourth extending portions extends from the second padelectrode to a distal end without branching.
 42. The light emittingelement according to claim 21, wherein: in the plan view: the firstextending portion extends from the first pad electrode to a distal endwithout branching, each of the two second extending portions extendsfrom the first pad electrode to a distal end without branching, each ofthe two third extending portions extends from the second pad electrodeto a distal end without branching, and each of the two fourth extendingportions extends from the second pad electrode to a distal end withoutbranching.